This project will consist of three phases which will determine the ability of various experimental diagnostic techniques to measure early changes in enamel demineralization, to evaluate various interventions and to validate clinical diagnosis on exfoliated teeth from clinical studies. The diagnostic techniques to be evaluated are quantitative light-induced fluorescence (QLF), electrical conductivity (ECM), infrared light fluorescence (IR), and traditional visual evaluation. Phase I will validate both primary and secondary caries-like lesions that will be created in enamel specimens and measured for initial tissue changes. The gold standard to be used as polarized light microscopy (PLM). A standard chemically buffered, dissolution system will be used to create smooth surface lesions, while the microbial caries model (Fontana et al., 1996) will be used to evaluate secondary caries. In this case, both amalgram and resin restorative materials will be used. It is hypothesized that the QLF, ECM and IR will perform as well if not better than standard diagnosis in detecting minimal changes in mineral content. The second and longer phase of this project will determine the efficacy of early interventions in both the primary and secondary models. The early interventions will be used to help prevent lesion formation or progression as well as to enhance remineralization. In situ model systems will be used to determine the efficacy of fluoride treatments, remineralization agents and laser treatments on smooth surface caries. This model allows interaction between host, microflora, diet and interventions. The in vitro secondary caries model of Fontana will also evaluate the ability of early interventions such as CHX varnishes, fluorides, lasers, etc. to prevent, arrest and/or reverse secondary caries lesion formation. These studies will investigate the use of amalgram, glass ionomer, and composite as restorative materials. It is hypothesized that early intervention will prevent overt lesion formation that requires operative intervention. The third Phase consists of using PLM as the gold standard for determination of the extent of lesion formation in exfoliated teeth. These teeth will be collected in Projects II and II and sent to Iowa for evaluation. Teeth used in the secondary caries model will also be evaluated with PLM and compared to CFSM. The laboratory and clinical data will be correlated by the Biostatistics Core.